The present invention relates to door locks, and more particularly to an assembly and method for preventing a battery fire originating in an electronic door lock.
Electronic door locks, as opposed to pure mechanical locks, need a power source to operate the locking and control mechanism. In battery operated electronic door locks, power is obtained from a set of batteries installed in the lock. The most commonly used batteries in electronic door locks are alkaline batteries. The service life (the time after which the batteries need to be replaced) depends on the usage of the lock, but is typically two to three years for normal usage doors. More recently, attempts have been made to increase battery life by incorporating other types of battery technology including lithium battery technology. However, practical application of lithium battery technology in electronic door locks has failed due in part to the technology's adverse affect on the integrity and specifications of fire rated doors. Lithium batteries adversely affect the integrity and specifications of fire rated doors because the batteries can experience severe outgassing of flammable gases and violently deflagrate when exposed to elevated temperatures achievable during a building fire. The violent deflagration of lithium batteries has the undesirable effect that it can cause the fire on one side of the fire rated door to propagate to the other side and hence compromise the intended function of a fire door. A circuit board commonly utilized in electronic door locks is commonly one of the first components to catch fire and act as a potential ignition source for constituents outgassed from the venting of lithium batteries.